What Falling Oil Prices Are Doing To America's 10 Richest Oil Tycoons

David Koch in New York. Jamie McCarthy/Getty Images You win some, you lose some.

As oil prices continue to fall, some of America's richest oil tycoons have stayed on top and continued making money — while others have seen their fortunes cut in half.

According to Wealth-X, four of the top 10 oil billionaires have actually increased their net worth since oil prices started to decline last year.

David and Charles Koch top the list with a 7% increase in net worth since June, which Wealth-X attributes to the diversification of their company's investment portfolio. Elaine Marshall, who holds about 15% of Koch Industries, saw her net worth increase by 6%. Richard Kinder of Kinder Morgan Partners increased his net worth the most, by 23%.

The biggest loser among the top 10 by far was Continental Resources CEO Harold Hamm, currently caught in a bitter and costly divorce battle, who lost 50% of his net worth since June. Sisters Milane Frantz, Randa Williams, and Dannine Avara of the Duncan energy empire all saw their net worth decline by 11%.